Hydraulic impact tool



Oct. 17, 1961 s. L. CHRISTENSEN HYDRAULIC IMPACT TOOL 2 Sheets-Sheet 1 Filed NOV. 4, 1959 INVENTOR. SHELDON LCHRISTENSEN ATTORNEY Oct. 17, 1961 s. L. CHRISTENSEN 3,004,523

HYDRAULIC IMPACT TOOL 2 Sheets-Sheet 2 Filed Nov. 4, 1959 INVENTOR SHELDON L. CHRISTENSEN WMQW ATTORNEY Filed Nov. 4,1959, Ser. No. 850,849

' 6 Claims. (Cl. 121-28) 1 This invention relates to an impact tool of the type which may be used as a jack hammer, dirt tamper, post driver and similar operations in which a reciprocating pounding or driving action is required. Still more particularly this invention relates to an impact tool which is hydraulically operated and which may conveniently be operated, for example, by the hydraulic system of conventional type tractors or other motive vehicles.

The main object of the present invention is to provide a hydraulic impact tool, which for convenience of description will be described in relation to a hydraulically operated jack hammer, of a new and relatively simple construction. The hydraulic impact tool will be a self contained unit which may operate from any type of hydraulic system having a pressure line and a return line. Consequently, it may be presumed that the impact tool will find its greatest use in combination with a tractor having a hydraulic system as a part of its structure.

A further object of the present invention is to pro vide a hydraulic impact tool featuring a cylinder having an anvil at one end which strikes the shank of the working tool. The anvil is struck by the hammer endofa p'iston contained in the cylinder. It is proposed to provide a communicating line between opposite ends of the cylinder and a check valve within the line which relieves pressure in advance of the piston during its power stroke and permits a relatively large pressure build up in advance of the piston during its return stroke to thereby etfect a cushioning action of the piston during the latter stroke.

Other objects and advantages of the present invention will become apparent to those skilled in the art as the nature of the present invention is better understood from the following description and as shown in the accompanying drawings.

FIG. 1 is a side view of an hydraulically operated jack hammer.

'FIG. 2 is an enlarged vertical sectional view extending through the axis of the hydraulic jack hammer.

.FIG. 3 is a sectional view taken substantially alon the line =3--3 of FIG. 2. FIG. 4 is a schematic view of the hydraulic system in the jack hammer showing one position of the control valve and piston.

FIG. 5 is a view similar to FIG. 4 showing a difierent opening 14 which receives a reciprocating'piston 15 one endiof' which operates as a hammer. The housing or cylinder 13 is" closed at one end by a shank supporting portion 16and a head portion 17 at the opposite end,

the portions 16 and ,17bein g bolted as at 1 8, 19 to the housing13. Theshankqlz of the tool has a hexagonal' cross section which slides in a hexagonal bore in portion 16 of the; housing. Consequently the tool 10 is permitted grelatively free axial movement and is restricted :againstangular or. rotativev movement in the supporting portion 16. The tool 10 is further provided with an integral annular collar 20 which fits nited States Patent 0 33. Therefore, it becomes-obvious depressing the may move axially in an enlarged annular opening ,21 at the outer end of the support portion 16. A shoulder 22 limits inward axial movement of the tool 10. Extending outwardly from the collar 20 is an axial groove or slot 23 which receives a lug 24 pivotally mounted on the shank supporting portion 16 by means of a pivot pin 25. The lug 24 has an integral outwardly extending and hand Operated portion 26 which is utilized to raise or lower the lug 24 into and out of the slot 23. As may be easily visualized from viewing FIG. 2, the 'lug 24 may be raised clear of the annular opening 21 so as to permit the collar 22 to pass under the lug 24 for pur poses of removing or placing the tool 10 in or out of its operating position in the supporting portion 16. A spring 27 is provided to hold the lug 24 in its down position. The head portion 17 of the housing has radially projecting hand supports 30, 31 by which the operator may carry or direct the jack hammer. Pivoted at 32 on thehead end 17 is a control lever 33 which will, as later will become apparent, control the flow of hydraulic fluid into the jack hammer.

Provided adjacent the shank supporting end 16 of the main housing or body is an anvil 35 which has its main portion seated in the cylinder opening 14 and has an enlarged head or striking end 36 extending outwardly of the main body or support 13, the opening 14 of the main body 13 being there enlarged, as at 37, to receive the enlarged end 36. In registry with the enlarged opening 37 is an end opening 38 in the shank support 16. The openings 37, 38 combine to permit a limited amount of axial movement of the anvil 35.

As may be seen from viewing FIG. 2, the shank portion 12 of the tool extends into the opening formed by the recessed ends 37, 38 and is obviously positioned to receive the striking force of the anvil 35.

A bypass or communication duct 40 opens into the piston opening 14 at opposite ends of the cylinder 13, such being shown by the passages 41, 42 which extend radially from the main duct 40. A check valve 43 is provided inthe duct system for the purpose of permitting opening, is enlarged at 55 to "accommodate axial move-- ment of the enlarged section 52. Opening'into the enlarged opening 55 is a second check valve 56 which permits fluid to. flow from the passage '40 into the cylinder opening '14.

The main body of housing 13 has an outer surface which in cross section is inverted U'-shaped with a hori-; zontal flat surface 60 on its lower side. Bolted at 61, 62- toithe lower or under side 60 of the cylinder body 13 is a valve mechanism composed of ,a main valve casing 64 having an upper surface 65-lying adjacent tothe under surface 60 of the body 13, the two surfaces being sepa-" rated by a sealing gasket 66. The casing 64 is provided with a bore 66 having contained therein an axially shift able spool valve 59. A pair of hydraulic hoses including a pressure line 67 i and a return line 68 is coupled at 69, 70 to the under side of the casing 64 and open into an inlet line 71and a discharge or return line 72 respectively.

Provided in the inlet line 71 is a valve 73 which is biased by springs 74, to block off the passage 71. The valve 73 r is provided with a stem 75 which extends axially outwardv ly of the head 17- and is connected to the control lever 3,004,523 Patented Oct. 17, 1961 3 lever 33, the valve 73 will be moved axially to open the line 71 to the fluid passing through the inlet line 67.

The valve structure as well as the associated passages between the valve and cylinder. 14. is for the purpose of providing a constant reciprocating action of, the piston Afirstpairof axially oil-set fluid passages extends from. the casingto-the. cylinder 14. and opensinto the cylinder in: axialoff-set relation. The pair. of passages comprises a.

first. supply lineor passage 80 and a. first return passage 81 which opens into the cylinder 14 for purposes. of. supplying and. returning. fluid from. the reduced section 54 of. the. piston. A second. pair. of axially oflset passage.

leads. from: the. casing to. the cylinderf14, and opens into: the cylinder in axial ofi-set relation. The second pair of axially off-set passages includes. a'second supply line. or passage 82.andv a secondreturnpassage. 83 for supplying and returning. fluid from the second reduced. section 53 of: the piston. A third pair of fluid passages 84, 85 leads fromropposite-ends of the casing 64 into opposite endsof thecylinder 14.. The lines or passages 84, 85 open into the cylinder 14 adjacent the respective opposite piston ends 51,50 and. normally are. closed by. the respective piston ends. 51-, 50. except at the extreme terminal. endsof the piston strokes.

, Theshiftable valve spool 59 is composed oi three large spool knobs 8.6, 87, 8,8. separated by a pair'of recessed.

portions. 89, .90- The. fluid inlet 71 opens into the opening in the casing: formed by the recessed'portion 89 and.

the fluid returnline 72 opens into the opening formed by therecessedportion 9110f the valve spool 59. Itwill be noted that the. inlet passage. 71. opens into. the.- casing. cylinder adjacent the. reduced portion 89 of the spool.

valve 59 and also. the first andsecond. supply passages 80; 82. open into an. area. of the casing adjacent the 're-- cessed. portion 89.. The. discharge outlet 72; openstinto an area of the casing cylinder adjacent the recessediportion 90. of the. spool! 59 and. the return line..8.1, 83 also opens into. thecasing cylinder adjacent to. or approximate the recessed portion 9.0.of the spool59.

Referring specifically toFIGS. 4 and 5 for-explanation.

of the. operation of. the. mechanism, FIG. 4. shows the. mechanism. in a positionin which. thepiston has just. re-

versed its stroke: and .is. moving, in. the .initial stages .Qi. its

power stroke. The. spool 59. is. positioned. so. that the.

second fluid passage 82 is blocked on by the enlarged: spool-section 86:and fluid. from the. inlet 71.,is;passed.. adjacent the reduced section 89 of the spool illEQ ilhQrfiISlI.

fluidzsupply passage. 80 to be passed into. the. area adjacent thereducedpistonsection-54... The first return passage. 81; is: blocked: by the. enlargedspooh section 87 and. the second return passage.. 83s opens into: the. spool... cavity formed: by the. reduced section. 90. andconsequently fluidl may. passfrom aposition. in advanceof, the spindle section 52- throughthe return passage 83- andinto'the. outlet. line. 72.. Therefore, the:fluid.p assing through .thepressure lines. 71 and into the-first; supply. passage.80.to.be passedbehind.

the enlarged piston section 52.will causezthe:piston.15..to move: in itspower stroke tothe right. at: a..high..rate. of speed. until the strikingend 50.. of thepistonwcontactsthe anvil 35whichinturnstrikes thetool. 10. It -willi-be. noted 4 that the passages 84; 85:-are..open,,but. uponv slight. movement. of. the. piston, 15. to; the: rigth; both.

passages-will be. closed- Consequently the-valve 5-9- at: the initial stagesof the movement: of. the? piston 15.-to'2 theright istlockedagainstmovementa Referring now to FIG. 5, it will be noted that the anvil striking end 50 of the piston passes beyond the passage 85 thereby opening the passage 85 to the fluid contained in the recessed portion 53 of the piston. At the same time the discharge or return passage/83 is closed by the enlarged central section. 52' ofi the piston. llikewise, the head end ofthepiston will move in advance oi the control passage 84 at' the opposite-end of the cylinder. When the latter three stages occur; furtheradvance of the piston 15 will cause the fluid trapped. in the area. adjacent the reduced portion 53' to pass through the control passage 85 and to drive the spool 59 to the'left or from a position shown in FIG. 4 to a position shown in FIG. 5. Movement of the spool valve 59 to.a second position, as shown in FIG. 5, and as compared to its first position as shown in FIG.v 4, will permit communication between the third inlet 7'1.andv the second supply passage 82 while blocking. communication between the pressure inlet 71 and the first supply passage 80. Likewise, the. return passage 81 will be opento communicate with the discharge or re turn outlet 72 and the second discharge passage 83 will be blocked by the spool valve-59. Consequently there will be a pressure build up in the area to the right of'the enlarged central. section 52 of the piston which will'drive the piston. in itsreturn stroke to the left or to the head. of the cylinder. This movement to the left will continue. until the. opposite piston ends 51, 50 uncovers their respective control passages 84; 85 and the large central portion 52, of the piston covers thereturn passage 81',.or to a position shown in FIG. 4 at which time the fluid will be forced into the passage 84 by advance of the piston which will cause the spool valve 59 tomove fromthe postion shown in FIG. 5' to that shown in FIG. 4'. Therefore, it becomes apparent that there is continuous reciprocating action: of the piston 15 so.l'ongas the valve 73 is retainedopen.

It becomes apparent that there will be some fluid re.- tainedi'nthe casing at opposite ends ofthespool valve 59'- and in the passages 84, 85' and may leak or be discharged into opposite ends of the cylinder opening 14 in advance of the piston ends.50,.51. Due to the pressure created by the. movement ofthe piston 15'. the oil. will become generally vaporized and will enter. into the. passageor duct 40 from one end. through. the checkvalve 43 and at-. the other endthrough the opening 41. Uponthepiston head 50. movingto the.v right the oil in advance. of the piston head 50 will move into the passage 40 and into the. area of the. cylinder opening 14. adjacent. the. piston head-.51. Consequently, there .will be. no appreciatable-pressure build uprin. advance oh the. piston. in. the 'anvihstriking stroke. Upon the piston 15 moving te.-the,.left the. fluid or. vapor in. advance of thepiston-headlSI will-.move into .thepassage40 and since .it isblocked by. thecheck valve;

43 from entering the opposite end of the cylinder open? ing. 14-will. pass. througlr the check .valve.56' and into :the cylinder 13 adjacent the.piston.head..51. where: it willbe discharged. into. the return: passage 81.. Viewing FIG 4 it. becomes. apparent-thatthe. opening in .whichthe check. valve 56, is: disposed is. blocked from. entering into the cylinder opening. 14t.by..thev enlarged central. portion of the piston .52 as the piston moves to. its extremeterminalend .in its. movement-tov the left. At .thispointit becomes.

obvious thatalloutlets in .advance'of the pi'stonhead 51 have been,lilocked'and'consequently the pressure created in the cylinder openingiefin advance of'the. piston .head' 51 acts as a; cushion to'the piston 15in its return stroke.

While onl'y'one'fornr of theli nvention has been shown it should be recognized tliat 'otlier forms andvariations will occur to those skilled i in the art without" departing from the basic principles of the invention. Thereforewhile' the invention was shown and describedin detailfor the purpose of clearly'and concisely. illustratingth'eprinciples, thererisnorintentiom to'limit or'narrowtlre inventionbeyondithe liroad concepts set forth :iir-the appendedclaims.

7 What is claimed is:

1. A hydraulic impact tool comprising a main body having a shank support, a toolhaving a shank carried by said shank support, said body having a cylinder, an anvil alined with said support to strike the shank, a hammer in said cylinder for striking said anvil, a piston movable with said hammer, a spool valve casingjhaving hydraulic pressure inlet and return ports, pressure and returnpassageways extending between the casing and .cylinder adapted to be connected to said inlet and return ports re spectively during the actuation of said piston; spool-control fluid passageways communicating between opposite ends of the cylinder and opposite ends of the casing, a spool valve carried in said casing for directing liquid under pressure into one of said pressure passageways when said piston is in a raised position so that liquidunder pressure may enter said cylinder and drive said piston in a power stroke during which the return port is open to a return passageway to exhaust and return most of the'liquid in advance of said hammer, said piston closing said return passageway near the end of the power stroke of said hammer to form a pressure build-up in advance of said piston and opening a spool control passageway in advance of the piston to effect shifting of the spool valve to eifect opening of the return port to the other of the return passageways and the pressure port to the other of the pressure passageways while closing the pressure passageway and the return passageway effecting the power stroke of the piston, the shifting of the spool valve thereby effecting reversal of movement of the piston to its non-power stroke, said piston advancing in its non-power stroke to close said other of the return passageways to effect a pressure buildup in advance of the piston while opening the other of the spool-control fluid passageways to reverse shift the spool valve to the position eflecting the power stroke of the piston, and a fluid duct communicating between opposite ends of the cylinder and containing check valves therein for relieving pressure Within the cylinder and in advance of the hammer during the latters power stroke and retaining pressure within the cylinder in advance of the piston during the latters non-power stroke.

2. A hydraulic impact tool comprising a main body having a shank support, a tool having a shank carried by said shank support, said body having a cylinder, an anvil alined with said support to strike the shank, a hammer in said cylinder for striking said anvil, a piston movable with said hammer, a spool valve casing having hydraulic pressure inlet and return ports, pressure and return passageways extending between the casing and cylinder adapted to be connected to said inlet and return ports respectively during the actuation of said piston; including a first combination of pressure and return passageways effective to move the piston in its power stroke toward the anvil and a second combination of pressure and return passageways effective to move the piston in its opposite non-power stroke; a pair of valve-control fluid passageways communicating between opposite ends of the cylinder and opposite ends of the casing, a spool valve carried in said casing for directing liquid under pressure into and movable to one position to effect communication between the inlet and return ports and the first combination of pressure and return passageways so that liquid under pressure may enter said cylinder and drive said piston in a power stroke, said piston closing the return passageway near the end of the power stroke of said hammer to form a pressure buildup in advance of said piston and opening a spool control passageway in advance of the piston to eflt'ect shifting of the spool valve to a second position to effect communication between the second combination of pressure and return passageways and the inlet and return ports, the shifting of the spool valve thereby eifecting reversal of movement of the piston to its non-power stroke, said piston advancing in its non-power stroke to close said other of the return passageways to etfect a pressure build-up latters powerstro'ke and retaining pressure Within the cylinder in advance of the piston during the latters nonpower stroke. v r

3. A hydraulic tool comprising: an impact tool having ashank portion; a main .body definingla'hydraulic cylinder and having one end thereof supporting the shank of the impact tool for axial movementran anvil supported at the one end and alined with the shank for striking the latter; a piston having an anvilrstriking end, an opposite end, and a central portion, said ends and central portion being separated by first and second fluid-receiving reduced sections; a valve including a valve casing connected to the main body and having a valve'bore and an axially shiftable spool valve member contained therein, said casing having a pressure inlet and outlet, a first pair of axially offset passages leading from said casing to said cylinder and opening into the cylinder in axial otiset'relation comprising a first supply passage and a first return passage for supplying and returning fluid from said first reduced section of the piston, a second pair of axially oifset passages leading from said casing to said cylinder and opening into the cylinder in axial oifset relation including a second supply passage and a second return passage for supplying and returning fluid from said second reduced section of the piston; and a third pair of fluid passages leading from opposite ends of the casing to the cylinder and opening into the cylinder adjacent respectively the anvil-striking end and head end of the piston whereby said latter passages are normally blocked by said ends and are open to communication with the respective reduced sections of the piston at the terminal ends of the piston stroke to thereby eflect axial shifting of the valve; said valve member having thereon a plurality of'axially spaced -passage-controlling portions and shiftable axially in the easing between a first position in which the first supply passage and said second return passage are in communication with the fluid inlet and outlet respectively and said second supply passage and said first return passage is blocked to thereby effect the anvil-striking stroke of the piston and a second position in which the second passage and said first return passage is in communication with the fluid inlet and outlet respectively and said first supply passage and said second return passage is blockedto thereby efiect the return stroke of the piston; a communicating duct between the anvil end and head end of the cylinder; and check valve means in the duct permitting flow of fluid in the duct during the anvil-striking stroke ofthe piston and preventing flow of fluid inthe duct during the'return, effect a pressure build-up) stroke of the piston to thereby in advance of the piston in its return stroke;

4. A hydraulic tool comprising: an impact tool hav-fl ing a shank, portion; a main body defining 'a hydraulic' cylinder and having one end thereof snpportingthe shank of the impact tool for axial movement; an anvil supported at the one end and alined with the shank for striking the latter; a piston having an anvil-striking end, an opposite end, and a central portion, said ends and central portion being separated by first and second fluidreceiving reduced sections; a valve including a valve casing connected to the main body and having a valve bore and an axially shiftable spool valve member contained therein, said casing having a pressure inlet and outlet, a first pair of axially oflset passages leading from said casing to said cylinder and opening into the cylinder in axial offset relation comprising a first supply passage and a first return passage for supplying and returning fluid from said first reduced section of the piston, a second pair of axially ofiset passages leading from said casing to'said eylinder'and' opening into the-cylinder in axialofli: set relation including a second supply passage and asec-- ond return passage for supplying and returning: fluid from said second reduced section of the piston, and a third pairof fluid passages" leading from opposite ends of the' casing to the cylinder. and opening into the cylinder adjacent respectively the anvil=striking end andhead endof. the piston whereby said latter passages are normally blocked by said ends and are open to communication with the; respective reduced. sections ofthe piston at the terminal ends of the piston stroke to thereby efiect' axial shifting of. the valve; said valve member having thereon a plurality of axially spaced passage contr'olling portions and shiftableaxially in the casing. between: a" first position in which the first supply passage and said second return passage are in communicationwith the fluid inlet and outlet respectively and said secondsupply passage and said first return passage is blocked to thereby efiect the anvil-striking stroke of thepiston and asecond' position in which the second passage and saidfirst return passage is in communication with the fluidinletand outlet re-' spectively' and said first supply passage and said second return passage is blocked to thereby efiect thereturn stroke of the piston; a communication duct between the anvil endand head of the cylinder to relieve pressure build-up in advance ofthe piston.

5. A hydraulic tool comprising: an impact-tool: having a shank portion; a main bodydefining a hydraulic cylinder and having one end thereof supporting the shankof the impact tool for axial movement; an anvil supported at the one endand alined with the shank for striking the latter; a piston having an anvil-striking end, an opposite end, and a central portion, said ends and central portion being separated by first and second fluid-receivingreduced sections; a valve including a valvecasing connected to the main body and having a valve bore and an axially shiftable spool valve member contained therein said, casing; having a pressure inletpassageand outlet passage, a first pair. of axially offset passages leading from-said cas ing to'said cylinder and openinginto the cylinder in axial ofi'set relation comprising a first supply passage and a first return passage for supplyingand returning; fluid from; said first reduced sectionoft-he piston, a=second pair of axiallyoffset passages leading from saidcasing; to said cylinder andopeninginto the cylinder in axial ofiset rela-- tion including a second supply passage and a second return passage for supplyingand. returning fluid irom said second'reduced section of? the pistomand a third pair of fluid passages leadingfrom opposite ends of the casing=to the cylinder and opening. into the cylinder adjacenttrespectively the anvil striki'ng endandhead endofthepiston wherehysa'id latter passages. are normally blocked by said ends and'are open to communication with the respective reduced sections of the piston at" the terminal ends of the piston stroke 't'o' thereby. elfect axial shifting of the valve; saidvalve ru'emhefhaving thereon a plurality'of axially, spaced. passage=oontrollingl portionsjan'd sh'iflable axially in: the casing'betwee'n afir'srpositien iii which the first supply passage" and said" second returnipassage are in communication'witli the flilid ili'let 'a'il d o'litlt respectively and said second supply passage and saidfir'sf return passage is blocked: to thereby e'ifect the anvil-striking stroke of th'e piston and a second position in which the second passage aridsaid firstretnrn passage is in communication withth'e flhid inlet and outlet respectively and said first supply-- passage and said second return passage is blocked to thereby efiect the return stroke of the. piston; communicating' duct means between the' anvil en'd of the cylinder and the outlet passage effective" to relieve pressure buildin advance ofthe piston in its anvil striking stroke.

6; A hydraulic'tool'comprising: an impact t'ool having a shank portion; a main bodydefining-a hydraulic cylinder and having one end thereof supportinglthe shank of the impact tool for axial movement; an anvil supported at the one endand alined with the shank for striking the latter; a piston having an anvil-striking end, an opposite end-,1 and a central portion, said ends and central portion being separated by firstand second fluid receiving reduced sections; a-valve including a valve casing connected to the main body and having a valve bore and an axially shiftable spool valve" member contained therein, said casing: having a pressure inlet passage and outlet passage, a firstpair of axially ofise't passages leading from said casing to said'cylinder and opening into the cylinder in axial ofiset relation comprisingafirst supply passage and a first return passage'for supplying and returningfluid'from said first reduced section of the piston, 21 second pair of axially ofiset-passages leading from said casing to said cylinder and opening into the cylinder in axial offset relation including; a second supply passage and a second return passage for'supplying and returning fluid from said-sec 0nd reduced section of the piston, and a third pair of fluid passages leading from opposite ends ofthe casing to the cylinder and opening into the cylinder adjacent respectively the anvil-striking end and head end of the piston whereby said'latter passages are normally blocked by said ends and are open to communication with the re-' sp'ec'tive reduced sections ofthe piston at the terminal ends of the pistonstr'o ke to therebyefi'ect axial shifting of the valve; andsaid valve member having thereon a plurality of axially spacedpassage-controlling. portions and shiftable axially in;the casing between a first position in which the first supply passage and said second return passage are in communication with the fluid inlet andoutlet respectively and said: second supply passage and said firstreturn passage is blocked to thereby effect the anvil-striking stroke-ofthe piston and a secondposition in which the second passager and said first retuin passage is in communication with-thefiuid'inlet and outlet respectively andsaidfirst-su pply passage and said second return passage'is'blocked to" thereby efiect the return stroke of the piston:

liet'rences Cited in the file of this patent UNITED STATES PATENTS 1,050,287] Qlson'p... Jan. 14, 1913 1,429,786 snnrn Sept; 19, 1922 l,7l l;',8ll' Rudlin July 7; 1929 ou 2332,51 4 Da-y Feb. 18, 1941 

